The present invention relates to a device embedded in a concrete slab to drain moisture which accumulates between a watertight isolating layer applied to the concrete slab and the surface of the concrete slab proper, and/or moisture which permeates a surface layer deposited on top of the isolating layer. The device comprises a drainpipe which is embedded in the concrete and into the open upper end of which a shallow funnel is inserted in a manner as to be flush with the upper surface of the concrete slab. The upper portion of the funnel is provided with radially extending grooves and the funnel opening is covered with a mushroom shaped insert or liner resting on the isolating layer and having radially extending grooves in its underside. The lower end of the drainpipe is supported in an outlet or discharge socket installed in the concrete slab so as to be flush with the underside thereof. The outlet socket is provided with a drip collar.
The field of use for such drainage devices is primarily in civil engineering, particularly in bridges and overpasses. The layer deposited on top of the isolating layer is then in most cases a roadway surface layer.
Drainage devices are disclosed in German published patent application DE-OS 21 35 314. In actual practice, however, it has been found that the disclosed device has severe disadvantages. The drawing of the published patent application shows water drops which fall in an exactly centralized relation to the drainpipe. Such theoretical assumption, however, has proven erroneous as practical experience has shown. Rather, the water runs from the outer edge of the funnel-shaped insert down into the funnel tube along the interior wall surface. The water is not conducted from the wall surface over the supporting ribs of the stem to the top or cap of the mushroom shaped cover. Due to the surface tension of the water and the vibrations of the bridge caused by the traffic rolling over it, the minimal gap between the inner wall surface of the annular groove and the interior wall surface of the drainpipe is quickly bridged, favoring the run-off of the water down the inner wall surface of the drainpipe. The consequences, particularly the obstruction of the pipes by lime deposits, are all too familiar. In winter, long hazardous icicles form at the outlets of such drainpipes.